We don't really have a budget, it's more about what I think is appropriate. They get one present from santa and one from us plus stocking. Occasionally there is an extra gift. My kids are five now (twins) as an idea this is the list of presents they've received each Christmas.
Ten months old- toy blocks, fancy vegetable dye made in Germany. About 50 euros. Toy duck on a stick, the legs flap as you push it, maybe 15 euros. No extra present this year as babies wouldn't know.
1 year old- brio train set and some toddler musical instruments (xylophone, tambourine etc) not sure how much I spent, the train set was ridiculously cheap, under 30-one of those Groupon deals. They only got the two presents as again toddlers wouldn't understand the concept of santa. I probably spent around 50/60 this year.
2 years old. Dolls house, playmobil fire truck (aldi has awesome gifts! ) I think there was something else this year but I can't remember.
3 years old -Anna and elsa dolls, elsa lego castle and ariel lego castle. They also got lego advent calendars. I spent around $180 this year on both of them. I shouldn't have bought them regular lego this early as they mostly just took it apart and insisted I put it together again. The lego castles are really neat though and they literally play with them for hours each day now at 5. The lego advent calendars are expensive but I buy them post Christmas, they don't know or care they're getting the previous years calendar.
4- cash register, doll prams, one twin got a tea set and the other got a baby princess tiana doll. Cash register was around 50 euros (wooden one I bought in a classic European toy shop) the prams were 20 dollars each, tea set was 10 and the darn tiana doll ended up being around 80 as they don't sell them in Australia so I had to order from overseas. They had some nice stuff in their stockings too, little cooking aprons, spoons and whisks, Schleich animals, plus some good quality art supplies. So around 250/300 for altogether.
5 (this year) I bought the lego hospital $108 and ski lift $60 from santa, from us they will receive a children's cook book and an art book. Their stockings have underwear, bubbles, electric tooth brush, orange, mini puzzle, slinky, stationary and a drawing book.
As you can see some of their presents can be expensive and sometimes cheap. I don't think the value amount matters, my daughter got just as much joy from her $10 aldi children's tea set as her sister did from her $80 tiana doll. Perhaps more, that kid is obsessed with entertaining. I give them the one gift I know they really want and so far they haven't been expensive (it was me who decided to buy the lego castles at three years old-they just wanted the dolls that were $30 for the two) I find setting a dollar amount as useless. If your child only wants a $10 toy are you purposefully going to spend an extra $140 if you budgeted $150? Seems crazy and consumerist to me.